Oxidation electrode for water treatment and water treatment system including the oxidation electrode

Abstract

According to a specific embodiment of the present invention, there is provided an oxidation electrode for water treatment, the oxidation electrode for water treatment comprising: a current collector; an intermediate layer, the intermediate layer being arranged on the current collector and the intermediate layer being composed of a metal oxide; and an electrode active material coating, the electrode active material coating comprising an electrode active material in powder form. The current of the oxidation electrode for water treatment does not vary much over time, so it has the advantages of being stable and having a high removal efficiency of organic matter in the treated water.

Description

Technical Field

[0001] The invention relates to an oxidation electrode for water treatment and a water treatment system comprising the oxidation electrode. Background Art

[0002] As industry develops rapidly, wastewater properties are becoming more diverse, and difficult-to-degrade organic matter that cannot be treated by existing biological water treatment processes will cause environmental problems, thus posing a huge threat to the ecosystem. As an alternative, a technology that can oxidize and control organic matter in water systems by electrochemical methods is introduced. Since it does not use additional chemicals, it is attracting attention as a next-generation water treatment technology.

[0003] The manufacturing cost of electrodes used in electrochemical water treatment technology is high, so in order to reduce the cost, research related to manufacturing economical electrodes is being conducted.

[0004] In addition, since electrodes used in electrochemical water treatment technology are in direct contact with wastewater and may be oxidized, research is also being conducted to ensure the stability of the electrodes themselves.

[0005] [Prior art literature]

[0006] [Patent Document]

[0007] (Patent Document 1) JP 2020-194764 A Summary of the invention

[0008] Technical issues to be solved

[0009] The object of the present invention is to provide an oxidation electrode for water treatment and a water treatment system comprising the oxidation electrode.

[0010] Technical Solution

[0011] According to the first aspect of the present invention, an oxidizing electrode for water treatment includes: a current collector; an electrode active material coating, the electrode active material coating containing an electrode active material in powder form; and an intermediate layer, the intermediate layer is arranged between the current collector and the electrode active material coating, and the intermediate layer is composed of a metal oxide.

[0012] According to one embodiment, the current collector may include Ti.

[0013] According to a specific embodiment, the current collector may have a thickness of 0.25-2 mm.

[0014] According to a specific embodiment, the electrode active material may include boron doped diamond (BDD), a Magneli phase, a single atom catalyst, or a combination thereof.

[0015] According to a specific embodiment, the electrode active material in powder form may have a maximum dimension of 1 nm to 30 μm.

[0016] According to a specific embodiment, the electrode active material coating layer may have a thickness of 100 nm to 50 μm.

[0017] According to a specific embodiment, the metal oxide may include RuO 2 、IrO 2 , Pt, platinum oxide, TiO 2 or a combination thereof.

[0018] According to a specific embodiment, the intermediate layer may have a thickness of 10-1000 nm.

[0019] According to a second aspect of the present invention, there is provided a method for manufacturing the above-mentioned oxidation electrode for water treatment, the method comprising the following steps: providing a current collector; forming an intermediate layer on the current collector; and forming an electrode active material coating on the intermediate layer.

[0020] According to a third aspect of the present invention, there is provided a water treatment system comprising the above-mentioned oxidation electrode for water treatment.

[0021] Beneficial Effects

[0022] According to the present invention, it is possible to provide an oxidation electrode which can stably maintain current during water treatment and has a long life. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figures 1a to 1f is a cross-sectional image of an oxidation electrode for water treatment according to a specific embodiment of the present invention.

[0024] Figure 2 is a surface SEM image of an electrode active material coating layer according to a specific embodiment of the present invention.

[0025] Figure 3a to Figure 3c This is a graph comparing the change in current density when a voltage is applied using a predetermined oxidation electrode for water treatment according to one specific embodiment of the present invention and a comparative production example.

[0026] Figure 4is a graph comparing the total organic carbon (TOC) removal performance of different oxidation electrodes according to one embodiment of the present invention. DETAILED DESCRIPTION

[0027] The objects, advantages and features of the present invention will be more clearly understood through the accompanying drawings and the following detailed description and preferred embodiments, but the present invention is not necessarily limited thereto. In addition, in the process of describing the present invention, if it is considered that the specific description of the related known technology may make the main idea of ​​the present invention unclear, its detailed description will be omitted.

[0028] According to the present invention, there is provided an oxidation electrode for water treatment, the oxidation electrode for water treatment comprising: a current collector; an electrode active material coating; and an intermediate layer, the intermediate layer being arranged between the current collector and the electrode active material coating. The oxidation electrode for water treatment according to the present invention has Figures 1a to 1f The stacked structure shown.

[0029] The current collector is a support that can fix the active material, and plays a role in transferring charge to and from the water system in the electrochemical oxidation and reduction reaction when a voltage or current is applied. When an oxidation reaction occurs in the active material coating of the oxidation electrode, electrons move to the current collector through the active material coating, and the electrons transferred to the current collector can undergo a reduction reaction on the surface of the reduction electrode again in the water system through an external channel. Considering the function of the current collector as described above, it is advantageous for the current collector to have a low resistance.

[0030] In a specific embodiment, the current collector may include Ti, stainless steel, or a combination thereof. Preferably, the current collector may include Ti, and Ti has the advantages of low resistance and being conducive to transferring electrons.

[0031] In a specific embodiment, the current collector may have a thickness of 0.25-2 mm. When the thickness of the current collector is less than 0.25 mm, the electron transfer from the electrode active material coating of the oxidation electrode to the current collector is not smooth, and the electrochemical reaction may not easily occur even when a voltage is applied to the electrode. When the thickness of the current collector exceeds 2 mm, there is a problem of difficulty in thinning the electrode. In a specific embodiment, the current collector may preferably have a thickness of 0.25-1.0 mm, and more preferably may have a thickness of 0.25-0.5 mm.

[0032] The water treatment oxidation electrode includes an electrode active material coating, which plays the following role: when voltage is applied to the electrode, the electrode active material coating directly receives electrons from organic matter in the water system on the surface and oxidizes it, or indirectly generates oxidizing substances and uses them as a medium to oxidize the organic matter.

[0033] The electrode active material coating comprises an electrode active material in powder form. More specifically, the electrode active material coating of the present invention can be formed by an electrode active material in powder form. Due to the size limitation and cost issues of the synthesis reactor, the electrode active material coating of the oxidation electrode is difficult to be made into a large-area film form, and direct synthesis on the intermediate layer is also not easy in terms of process composition. The electrode active material coating of the present invention is manufactured by making the electrode active material into a powder form rather than a film form and fixing it on the intermediate layer, so the advantage is that it can have a large surface area without being limited by the manufacturing cost, process and reactor as described above.

[0034] In a specific embodiment, the electrode active material coating layer may include a conductive binder that forms a bond between powdered electrode active materials included in the electrode active material coating layer while firmly adhering the powdered electrode active materials bonded to each other to the intermediate layer.

[0035] In a specific embodiment, the electrode active material may include boron-doped diamond (BDD), Magnelli phase, single atom catalyst or a combination thereof. The electrode active materials listed above have high chemical stability and will not be oxidized and directly consumed even when an electric current is applied. In addition, the electrode active materials listed above have high electrical conductivity, which can cause the organic matter in the treated water to undergo electron transfer reaction on the surface of the electrode active material layer or effectively generate oxidizing substances, which can ultimately make the oxidation of the organic matter in the treated water easy.

[0036] In a specific embodiment, the electrode active material can be a state loaded on carbon black or activated carbon. When the electrode active material is a single atom catalyst, it does not exist in a single atomic state, but exists in a state loaded on a carrier, so that it can show electrical activity. In terms of not damaging the electrical activity of the single atom catalyst, the carrier is preferably a material with high electrical conductivity such as carbon black or activated carbon.

[0037] In a specific embodiment, the electrode active material coating may have a thickness of 100nm to 50μm. When the thickness of the electrode active material coating is less than 100nm, the degree to which the oxidation electrode withdraws electrons from the organic matter in the treated water may not be sufficient to oxidize and decompose the organic matter, and when the thickness of the electrode active material coating exceeds 50μm, the increase in the ability to oxidize organic matter is low compared to the cost of manufacturing the electrode active material coating, and therefore may not be cost-effective. In a specific embodiment, the electrode active material coating may preferably have a thickness of 200nm to 30μm, and more preferably may have a thickness of 500nm to 10μm.

[0038] In a specific embodiment, the electrode active material in powder form may have a maximum size of 1 nm to 30 μm. Wherein, the term "maximum size" refers to the maximum diameter of the diameter of the cross section of the electrode active material in powder form. The electrode active material in powder form has a small maximum size as described above, so that the effective surface area of ​​the oxidation electrode can be maximized, and a higher organic matter decomposition efficiency can be achieved compared to an oxidation electrode having a surface that is a plane of the same size. In addition, when the maximum size of the electrode active material in powder form is less than 1 nm and is too small, it will hinder the electrical contact between the organic matter in the treated water and the surface of the oxidation electrode, so that the organic matter decomposition efficiency may be reduced.

[0039] The water treatment oxidation electrode includes an intermediate layer disposed between the current collector and the electrode active material coating. The intermediate layer plays a role in protecting the current collector and preventing the conductivity from being reduced due to the ohmic contact between the current collector and the electrode active material coating. Specifically, the intermediate layer prevents the following problems: when a portion of the current collector of the water treatment oxidation electrode is exposed to the electrolyte in the treated water, a metal oxide as a non-conductor is formed at the interface of the current collector and the electrode active material coating due to the application of current, thereby generating high resistance inside the electrode or the oxidized current collector being dissolved and damaging the electrode stability.

[0040] The intermediate layer is composed of a metal oxide. Therefore, the intermediate layer will not be oxidized and dissolved even when exposed to an electrolyte, thereby preventing direct contact between the current collector and the electrode active material coating. In addition, the intermediate layer of the present invention can have the following advantages: by selecting an appropriate metal oxide and selecting an appropriate metal layer thickness for maintaining a distance from the current collector that transfers the charge, even a metal oxide will not reduce the conductivity of the electrode.

[0041] In a specific embodiment, the metal oxide may include RuO 2 、IrO 2 , Pt, platinum oxide, TiO 2 or a combination thereof. The metal oxide as described above has high electrical conductivity even as an oxide, and therefore does not reduce the electrical conductivity of the oxidation electrode when constituting the intermediate layer. In addition, the metal oxide is stable as an oxide and does not dissolve even when power is applied. In terms of maintaining the electrical conductivity of the oxidation electrode, the metal oxide is most preferably RuO 2 .

[0042] In a specific embodiment, the intermediate layer may have a thickness of 10-1000nm. The intermediate layer is composed of a metal oxide, which has high oxidation stability as described above, so even with a thin thickness, the direct contact between the current collector and the electrode active material coating can be completely blocked when the current is applied. When the intermediate layer has a thickness of less than 10nm, the direct contact between the current collector and the electrode active material coating cannot be completely blocked, which may damage the stability of the oxidation electrode. When the intermediate layer has a thickness of more than 1000nm, the electrical conductivity of the oxidation electrode may be reduced due to the resistance of the intermediate layer itself. In a specific embodiment, the intermediate layer preferably has a thickness of 20-500nm, and more preferably has a thickness of 50-100nm.

[0043] In a specific embodiment, the ratio of the thickness of the intermediate layer to the thickness of the current collector may be 1:100 to 20:100. When the above ratio is less than 1:100, the conductivity of the oxidation electrode may be reduced due to the ohmic contact between the intermediate layer and the electrode active material coating. When the above ratio exceeds 20:100, the conductivity of the oxidation electrode may be reduced due to the resistance of the intermediate layer itself. In a specific embodiment, the ratio of the thickness of the intermediate layer to the thickness of the current collector may preferably be 3:100 to 17:100, and more preferably 6:100 to 15:100.

[0044] According to one aspect of the present invention, a method for manufacturing the above-mentioned oxidation electrode for water treatment is provided, the method comprising the following steps: providing a current collector; forming an intermediate layer on the current collector; and forming an electrode active material coating on the intermediate layer.

[0045] In a specific embodiment, the step of providing a current collector may include a current collector surface purification step. Since the provided current collector is exposed to the air, it may contain trace amounts of non-conductive metal oxides, which are non-conductors and increase the resistance of the oxidized electrode. The surface purification step is a step of removing trace amounts of non-conductive metal oxides formed as described above, and the method is not limited as long as the non-conductive metal oxides on the current collector can be removed. As an example, the surface purification step can be performed by immersing the non-conductive layer in a high-temperature acidic solution.

[0046] In a specific embodiment, the step of forming an intermediate layer on the current collector may include the step of spraying, spin coating or brushing a substance for forming the intermediate layer on the current collector. The substance for forming the intermediate layer may include a metal salt, an acidic solution and distilled water as a precursor of a metal oxide constituting the intermediate layer, and these substances can be applied to the current collector by spraying, spin coating or brushing. After coating, after drying and heat treatment, the intermediate layer composed of the metal oxide as described above is formed on the current collector.

[0047] In a specific embodiment, the step of forming an electrode active material coating on the intermediate layer may include the step of spraying an electrode active material solution on the intermediate layer. The electrode active material solution contains the above-mentioned electrode active material in powder form and also contains a binder and a solvent, and the electrode active material solution is dispersed on the intermediate layer by spraying to form an electrode active material coating. In a specific embodiment, the step of forming an electrode active material coating on the intermediate layer may include the following steps: spraying the electrode active material solution on the intermediate layer so that the electrode active material per unit area (cm 2 ) contains 3-10 mg of electrode active material in powder form.

[0048] According to one aspect of the present invention, there is provided a water treatment system including the above-mentioned oxidation electrode for water treatment. The water treatment system includes: an electrode part, the electrode part includes the above-mentioned oxidation electrode for water treatment and a reduction electrode; a power supply part, the power supply part supplies power to the electrode part; a reaction part, the reaction part contains treated water containing organic matter, and makes the treated water contact with the electrode part, and the reaction part includes an inlet that allows the treated water to flow into the inside of the reaction part and an outlet that discharges the treated water from which the organic matter is removed to the outside of the reaction part. Due to the stability of the above-mentioned oxidation electrode for water treatment, the water treatment system has a long electrode replacement cycle, and therefore has an advantage in terms of system maintenance costs. In addition, due to the high conductivity of the above-mentioned oxidation electrode for water treatment, the water treatment system can exhibit a high organic matter decomposition efficiency compared to the supplied power.

[0049] Preferred embodiments are presented below to help understand the present invention. However, the following embodiments are provided only to make the present invention easier to understand, and the present invention is not limited thereto.

[0050] Manufacturing Example: Manufacturing of Oxidation Electrode for Water Treatment

[0051] In order to remove metal oxides that may be formed on the current collector, a current collector composed of Ti and having a size of 10 mm×20 mm×0.25 mm was immersed in a 10 wt % oxalic acid solution and heat-treated at a temperature of 80° C. for 1 hour.

[0052] Afterwards, Ru metal salt (RuCl 3 ) was dissolved in a solution of hydrochloric acid and distilled water in a weight ratio of 1:1 to prepare a Ru metal precursor solution. The precursor solution was brushed on the above-mentioned current collector, then dried at room temperature, and then heat-treated at 450°C for 10 minutes. The brushing, drying and heat-treatment processes as described above were repeated 10 times, and then finally heat-treated at 450°C for 1 hour to form a RuO on the current collector. 2 The middle layer of the composition.

[0053] Afterwards, boron-doped diamond (BDD) powder was selected as the electrode active material in powder form, 20 mg of BDD powder was mixed with 80 μL of nafion binder and 2 mL of isopropanol to form a mixture solution, and the mixture solution was subjected to ultrasonic treatment (sonication) for about 1 hour so that the BDD powder was evenly dispersed in the mixture solution. The mixture solution prepared as described above was sprayed on the intermediate layer to manufacture an oxidation electrode for water treatment. The prepared oxidation electrode for water treatment has a surface area per unit area (cm 2 ) contains 5 mg of BDD powder. The entire cross-section of the prepared water treatment oxidation electrode is as follows Figure 1a As shown, the middle layer shows Figure 1b The thickness distribution of Ru and O in the intermediate layer is shown in Figure 1c and Figure 1d As shown, the distribution of carbon and boron in the electrode active material coating is as follows: Figure 1e and Figure 1f The BDD powder coated with the electrode active material shows Figure 2 Particle size shown.

[0054] Comparative Manufacturing Example 1

[0055] The oxidation electrode for water treatment was manufactured in the same manner as in the above manufacturing example except that the formation of RuO 2 The prepared oxidation electrode for water treatment is in a state where a mixture solution containing BDD powder is sprayed on a current collector, wherein the oxidation electrode for water treatment has a surface area (cm 2 ) contained 5 mg of BDD powder.

[0056] Comparative Manufacturing Example 2

[0057] The oxidation electrode for water treatment was manufactured in the same manner as the above manufacturing example, except that the mixture solution containing BDD powder was not coated on the intermediate layer. The manufactured oxidation electrode for water treatment only included the current collector and the intermediate layer, but did not include the electrode active material coating layer.

[0058] Experimental Example 1: Confirming stability by evaluating the change in current density of the electrode

[0059] The oxidation electrodes for water treatment of the manufacturing examples, comparative manufacturing examples 1 and comparative manufacturing examples 2 were immersed in 30 mL of an electrolyte containing 28 mg / L of TOC, and a constant voltage of 6 V was applied thereto. The constant voltage of 6 V was applied for 6 hours, and the change in current density during the electrochemical reaction between the oxidation electrode for water treatment and the electrolyte containing TOC was confirmed.

[0060] like Figure 3a As shown in FIG. 1 , it was confirmed that the current density of the oxidation electrode for water treatment of the manufacturing example was about 30 mA / cm during 6 hours. 2 , remain constant.

[0061] like Figure 3b As shown, it was confirmed that the current density of the oxidation electrode for water treatment in Comparative Production Example 1 dropped sharply in the initial stage (within about 5 minutes after voltage application), and the current density converged to 0 about 3 hours after voltage application.

[0062] like Figure 3c As shown, it was confirmed that the current density of the oxidation electrode for water treatment of Comparative Manufacturing Example 2 dropped significantly at the initial stage and then gradually dropped. The current density of Comparative Manufacturing Example 2 was higher than that of Comparative Manufacturing Example 1 but lower than that of the manufacturing examples.

[0063] From the above experimental results, it can be confirmed that when an electrode including all current collectors, intermediate layers and electrode active material coatings is used as an oxidation electrode as in the manufacturing example, at a constant voltage, the current density does not increase or decrease over time, but can maintain a constant high level of current density, and therefore has stability.

[0064] Experimental Example 2. Confirmation of TOC Control Performance of Each Electrode

[0065] The oxidation electrodes for water treatment of the manufacturing examples, comparative manufacturing examples 1 and comparative manufacturing examples 2 were immersed in 30 mL of an electrolyte containing 28 mg / L of TOC, and a constant voltage of 6 V was applied thereto. After applying a constant voltage of 6 V for 6 hours, the TOC change in the electrolyte was confirmed, and the results were as follows: Figure 4 shown.

[0066] See also Figure 4 It can be confirmed that when the oxidation electrode of the manufacturing example is used, the TOC removal rate is about 12%, when the oxidation electrode of the comparative manufacturing example 1 is used, TOC is not removed at all, and when the oxidation electrode of the comparative manufacturing example 2 is used, the TOC removal rate is about 3.8%.

[0067] This confirmed that the TOC removal rate was also the best when the oxidation electrode for water treatment including all the current collector, the intermediate layer and the electrode active material coating layer was used as in the manufacturing example.

[0068] From the two experimental results described above, it is concluded that, in view of the stability of the oxidation electrode and the organic matter removal effect, it is preferred to use an oxidation electrode for water treatment including all of the current collector, the intermediate layer, and the electrode active material coating.

[0069] The present invention has been described in detail above through specific embodiments. The specific embodiments are used to specifically illustrate the present invention, but the present invention is not limited thereto. It is obvious that those skilled in the art can make modifications or improvements within the scope of the technical concept of the present invention.

[0070] Simple modifications or improvements of the present invention all belong to the scope of the present invention, and the specific protection scope of the present invention will become more clear through the claims.

Claims

1. An oxidation electrode for water treatment, comprising: current collector; an electrode active material coating, the electrode active material coating comprising an electrode active material in powder form; as well as An intermediate layer is provided between the current collector and the electrode active material coating layer, and the intermediate layer is composed of a metal oxide.

2. The oxidation electrode for water treatment according to claim 1, wherein: The current collector includes Ti.

3. The oxidation electrode for water treatment according to claim 1, wherein: The current collector has a thickness of 0.25-2 mm.

4. The oxidation electrode for water treatment according to claim 1, wherein: The electrode active material comprises boron-doped diamond (BDD), Magneli phase, single atom catalyst or a combination thereof.

5. The oxidation electrode for water treatment according to claim 1, wherein: The electrode active material in powder form has a maximum size of 1 nm to 30 μm.

6. The oxidation electrode for water treatment according to claim 1, wherein: The electrode active material coating layer has a thickness of 100 nm to 50 μm.

7. The oxidation electrode for water treatment according to claim 1, wherein: The metal oxide comprises RuO2, IrO2, Pt, platinum oxide, TiO2 or a combination thereof.

8. The oxidation electrode for water treatment according to claim 1, wherein: The intermediate layer has a thickness of 10-1000 nm.

9. A method for manufacturing an oxidation electrode for water treatment according to any one of claims 1 to 8, comprising the following steps: providing a current collector; forming an intermediate layer on the current collector; as well as An electrode active material coating layer is formed on the intermediate layer. 10 . A water treatment system comprising the oxidation electrode for water treatment according to claim 1 .

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